From: SeongJae Park <sjpark@xxxxxxxxx> DAMON[1] can be used as a primitive for data access awared memory management optimizations. For that, users who want such optimizations should run DAMON, read the monitoring results, analyze it, plan a new memory management scheme, and apply the new scheme by themselves. Such efforts will be inevitable for some complicated optimizations. However, in many other cases, the users would simply want the system to apply a memory management action to a memory region of a specific size having a specific access frequency for a specific time. For example, "page out a memory region larger than 100 MiB keeping only rare accesses more than 2 minutes", or "Do not use THP for a memory region larger than 2 MiB rarely accessed for more than 1 seconds". This RFC patchset makes DAMON to handle such data access monitoring-based operation schemes. With this change, users can do the data access aware optimizations by simply specifying their schemes to DAMON. [1] https://lore.kernel.org/linux-mm/20200608114047.26589-1-sjpark@xxxxxxxxxx/ Evaluations =========== We evaluated DAMON's overhead, monitoring quality and usefulness using 25 realistic workloads on my QEMU/KVM based virtual machine running a kernel that this patchset is applied. DAMON is lightweight. It increases system memory usage by only -0.25% and consumes less than 1% CPU time in most case. It slows target workloads down by only 0.94%. DAMON is accurate and useful for memory management optimizations. An experimental DAMON-based operation scheme for THP, ‘ethp’, removes 31.29% of THP memory overheads while preserving 60.64% of THP speedup. Another experimental DAMON-based ‘proactive reclamation’ implementation, ‘prcl’, reduces 87.95% of residential sets and 29.52% of system memory footprint while incurring only 2.15% runtime overhead in the best case (parsec3/freqmine). NOTE that the experimentail THP optimization and proactive reclamation are not for production, just only for proof of concepts. Please refer to the official document[1] or "Documentation/admin-guide/mm: Add a document for DAMON" patch in the latest DAMON patchset for detailed evaluation setup and results. [1] https://damonitor.github.io/doc/html/latest-damos More Information ================ We prepared a showcase web site[1] that you can get more information. There are - the official documentations[2], - the heatmap format dynamic access pattern of various realistic workloads for heap area[3], mmap()-ed area[4], and stack[5] area, - the dynamic working set size distribution[6] and chronological working set size changes[7], and - the latest performance test results[8]. [1] https://damonitor.github.io/_index [2] https://damonitor.github.io/doc/html/latest-damos [3] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.0.html [4] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.html [5] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.2.html [6] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.html [7] https://damonitor.github.io/test/result/visual/latest/rec.wss_time.html [8] https://damonitor.github.io/test/result/perf/latest/html/index.html Baseline and Complete Git Tree ============================== The patches are based on the v5.7 plus v16 DAMON patchset[1] and Minchan's ``do_madvise()`` patch[2], which retrieved from linux-next/master and slightly modified for backporting on v5.7. You can also clone the complete git tree: $ git clone git://github.com/sjp38/linux -b damos/rfc/v12 The web is also available: https://github.com/sjp38/linux/releases/tag/damos/rfc/v12 There are a couple of trees for entire DAMON patchset series that future features are included. The first one[3] contains the changes for latest release, while the other one[4] contains the changes for next release. [1] https://lore.kernel.org/linux-mm/20200615161927.12637-1-sjpark@xxxxxxxxxx/ [2] https://lore.kernel.org/linux-mm/20200302193630.68771-2-minchan@xxxxxxxxxx/ [3] https://github.com/sjp38/linux/tree/damon/master [4] https://github.com/sjp38/linux/tree/damon/next Sequence Of Patches =================== The 1st patch allows DAMON to reuse ``madvise()`` code for the actions. The 2nd patch accounts age of each region. The 3rd patch implements the handling of the schemes in DAMON and exports a kernel space programming interface for it. The 4th patch implements a debugfs interface for the privileged people and user programs. The 5th patch implements schemes statistics feature for easier tuning of the schemes and runtime access pattern analysis. The 6th patche adds selftests for these changes, and the 7th patch adds human friendly schemes support to the user space tool for DAMON. Finally, the 8th patch documents this new feature in the document. Patch History ============= Changes from RFC v11 (https://lore.kernel.org/linux-mm/20200609065320.12941-1-sjpark@xxxxxxxxxx/) - Refine the commit messages (David Hildenbrand) - Clean up debugfs code Changes from RFC v10 (https://lore.kernel.org/linux-mm/20200603071138.8152-1-sjpark@xxxxxxxxxx/) - Fix the wrong error handling for schemes debugfs file - Handle the schemes stats from the user space tool - Remove the schemes implementation plan from the document Changes from RFC v9 (https://lore.kernel.org/linux-mm/20200526075702.27339-1-sjpark@xxxxxxxxxx/) - Rebase on v5.7 - Fix wrong comments and documents for schemes apply conditions Changes from RFC v8 (https://lore.kernel.org/linux-mm/20200512115343.27699-1-sjpark@xxxxxxxxxx/) - Rewrite the document (Stefan Nuernberger) - Make 'damon_for_each_*' argument order consistent (Leonard Foerster) - Implement statistics for schemes - Avoid races between debugfs readers and writers - Reset age for only significant access frequency changes - Add kernel-doc comments in damon.h Changes from RFC v7 (https://lore.kernel.org/linux-mm/20200429124540.32232-1-sjpark@xxxxxxxxxx/) - Rebase on DAMON v11 patchset - Add documentation Please refer to RFC v7 for previous history SeongJae Park (8): mm/madvise: Export do_madvise() to external GPL modules mm/damon: Account age of target regions mm/damon: Implement data access monitoring-based operation schemes mm/damon/schemes: Implement a debugfs interface mm/damon/schemes: Implement statistics feature mm/damon/selftests: Add 'schemes' debugfs tests damon/tools: Support more human friendly 'schemes' control Documentation/admin-guide/mm: Document DAMON-based operation schemes Documentation/admin-guide/mm/damon/guide.rst | 35 ++ Documentation/admin-guide/mm/damon/plans.rst | 23 +- Documentation/admin-guide/mm/damon/usage.rst | 127 ++++++- include/linux/damon.h | 66 ++++ mm/damon.c | 347 +++++++++++++++++- mm/madvise.c | 1 + tools/damon/_convert_damos.py | 128 +++++++ tools/damon/_damon.py | 146 ++++++++ tools/damon/damo | 7 + tools/damon/record.py | 139 +------ tools/damon/schemes.py | 109 ++++++ .../testing/selftests/damon/debugfs_attrs.sh | 29 ++ 12 files changed, 995 insertions(+), 162 deletions(-) create mode 100755 tools/damon/_convert_damos.py create mode 100644 tools/damon/_damon.py create mode 100644 tools/damon/schemes.py -- 2.17.1
